Move some of the code manipulating MCS nodes into separate functions.
This would allow easier integration of alternative ways to manipulate
those nodes.
Signed-off-by: Alex Kogan <alex.ko...@oracle.com>
Reviewed-by: Steve Sistare <steven.sist...@oracle.com>
---
kernel/locking/qspinlock.c | 48 +++++++++++++++++++++++++++++++++++++++-------
1 file changed, 41 insertions(+), 7 deletions(-)
diff --git a/kernel/locking/qspinlock.c b/kernel/locking/qspinlock.c
index 5941ce3527ce..074f65b9bedc 100644
--- a/kernel/locking/qspinlock.c
+++ b/kernel/locking/qspinlock.c
@@ -297,6 +297,43 @@ static __always_inline u32 __pv_wait_head_or_lock(struct
qspinlock *lock,
#define queued_spin_lock_slowpath native_queued_spin_lock_slowpath
#endif
+static __always_inline int get_node_index(struct mcs_spinlock *node)
+{
+ return node->count++;
+}
+
+static __always_inline void release_mcs_node(struct mcs_spinlock *node)
+{
+ __this_cpu_dec(node->count);
+}
+
+/*
+ * set_locked_empty_mcs - Try to set the spinlock value to _Q_LOCKED_VAL,
+ * and by doing that unlock the MCS lock when its waiting queue is empty
+ * @lock: Pointer to queued spinlock structure
+ * @val: Current value of the lock
+ * @node: Pointer to the MCS node of the lock holder
+ *
+ * *,*,* -> 0,0,1
+ */
+static __always_inline bool set_locked_empty_mcs(struct qspinlock *lock,
+ u32 val,
+ struct mcs_spinlock *node)
+{
+ return atomic_try_cmpxchg_relaxed(&lock->val, &val, _Q_LOCKED_VAL);
+}
+
+/*
+ * pass_mcs_lock - pass the MCS lock to the next waiter
+ * @node: Pointer to the MCS node of the lock holder
+ * @next: Pointer to the MCS node of the first waiter in the MCS queue
+ */
+static __always_inline void pass_mcs_lock(struct mcs_spinlock *node,
+ struct mcs_spinlock *next)
+{
+ arch_mcs_spin_unlock_contended(&next->locked, 1);
+}
+
#endif /* _GEN_PV_LOCK_SLOWPATH */
/**
@@ -406,7 +443,7 @@ void queued_spin_lock_slowpath(struct qspinlock *lock, u32
val)
qstat_inc(qstat_lock_slowpath, true);
pv_queue:
node = this_cpu_ptr(&qnodes[0].mcs);
- idx = node->count++;
+ idx = get_node_index(node);
tail = encode_tail(smp_processor_id(), idx);
/*
@@ -541,7 +578,7 @@ void queued_spin_lock_slowpath(struct qspinlock *lock, u32
val)
* PENDING will make the uncontended transition fail.
*/
if ((val & _Q_TAIL_MASK) == tail) {
- if (atomic_try_cmpxchg_relaxed(&lock->val, &val, _Q_LOCKED_VAL))
+ if (set_locked_empty_mcs(lock, val, node))
goto release; /* No contention */
}
@@ -558,14 +595,11 @@ void queued_spin_lock_slowpath(struct qspinlock *lock,
u32 val)
if (!next)
next = smp_cond_load_relaxed(&node->next, (VAL));
- arch_mcs_spin_unlock_contended(&next->locked, 1);
+ pass_mcs_lock(node, next);
pv_kick_node(lock, next);
release:
- /*
- * release the node
- */
- __this_cpu_dec(qnodes[0].mcs.count);
+ release_mcs_node(&qnodes[0].mcs);
}
EXPORT_SYMBOL(queued_spin_lock_slowpath);
--
2.11.0 (Apple Git-81)
